Earth Faults Flashcards
(7 cards)
State FOUR different causes of earth faults
- Sea Water Ingress
- Damaged Insulation
- Excessive Ambient Humidity
- Mechanical Damage
Explain how the fault is rectified
sea water ingress, damaged insulation, excessive ambient humidity, mechanical damage
Sea Water Ingress - Wash with distilled water and then dry thoroughly.
Damaged Insulation - Replace or Repair the insulation.
Excessive Ambient Humidity - Ventilate, in motors ensure heater is operational.
Mechanical Damage - repair or replace affected components.
with reference to earth faults on a ships electrical system
State how they are indicated
Three-Lamp Indication Method
- Three lamps are connected between each phase and earth through equal resistors.
NORMAL - All lamps glow equally
EARTH FAULT - The lamp connected to the fault goes dim or off, while the other two get brighter.
Instrument Type (Insulation Resistance Tester)
- Disconnect power, then use a tester between each phase and earth.
The phase showing low insulation resistance is the faulty one.
with reference to earth faults on a ships electrical system
Describe how the location is found
1), Process of Elimination
2), Using earth fault indicators on the switchboard.
3), Each circuit can be isolated to see if the fault disappears.
4), Before commencing this process all crew must be informed, as some circuits may be in use.
5), Once the faulty circuit is identified, an insulation resistance test can be carried out to pin point the specific machine.
with reference to earth faults on a ships electrical system
State the safety precautions necessary in order to carry out repairs
- Undertake a Risk Assessment
- Permit to Work
- Correct PPE is used
- Isolated and Tagged (lock out, tag out)
- Remove Circuit Breakers
- Prove Dead using live line tester
ADDITIONAL
State FOUR different causes of earth faults
- Sea Water Ingress
- Damaged Insulation
- Excessive Ambient Humidity
- Mechanical Damage
Explain how the fault is rectified
sea water ingress, damaged insulation, excessive ambient humidity, mechanical damage
Sea Water Ingress - Wash with distilled water and then dry thoroughly.
Damaged Insulation - Replace or Repair the insulation.
Excessive Ambient Humidity - Ventilate, in motors ensure heater is operational.
Mechanical Damage - repair or replace affected components.
